Rapid fluid administration is essential for patients suffering from shock, a life-threatening illness resulting from a variety of conditions including bacterial sepsis, hemorrhage, trauma, severe dehydration, and anaphylaxis. The American Heart Association's Pediatric Advanced Life Support (PALS) guidelines, the American College of Critical Care Medicine, and the Surviving Sepsis Campaign guidelines for adults recommend rapid fluid resuscitation as a key element of initial therapy. For example, PALS calls for 20 ml per kilogram of body weight to be infused over 5 minutes, and up to 60 ml/kg in the first 15 minutes.
In practice timely infusion of recommended fluid volumes is rarely achieved. This is often due to the difficulty of obtaining intravenous (IV) access in the setting of critical illness, and to the technical barriers to the infusion of large volumes of fluid. When IV access is difficult to obtain, the preferred technique is now intraosseous (TO) access, in which a needle is drilled directly into one of the long bones the arm or leg, and fluid is administered through the bone marrow into the central circulation. While IO infusion has revolutionized the approach to rapid access for fluid and medication administration in emergency medicine, it presents an additional challenge due to the resistance of the bone marrow, which makes rapid infusion of fluid difficult. These challenges are particularly common in children.
The increased resistance of bone marrow is similar to flow through small-bore or long IV catheters, and limits the ability of healthcare providers to deliver recommended volumes of resuscitation fluids rapidly.
Healthcare providers use several methods used to deliver fluid rapidly in these situations, include gravity, infusion pumps, pressure bags applied to the fluid reservoir, and hand-operated syringes, and mechanical rapid-infusion systems.
The fastest and most practical methods in higher-resistance situations are the hand-operated syringe techniques. The standard set of components used includes a fluid reservoir, a syringe, a three-way stopcock, and IV tubing linking these components with the IO or IV port. The user withdraws the plunger to fill the syringe from the fluid reservoir, turns the stopcock, and then depresses the plunger to drive the fluid through the IO or IV port and into the patient. The process is repeated multiple times until the desired volume has been delivered. Alternatively, one provider fills syringes from the IV fluid bag, while another connects the syringe, administers the fluid, disconnects the empty syringe, and repeats the process.
Both of these methods require emergency healthcare providers to either: 1) use great force with a large-volume syringe, often with two hands, and quickly resulting in user fatigue, or 2) to refill a small-bore syringe multiple times to achieve adequate volume, resulting in slow administration times and significant distraction for one or more workers. In either case two providers are often necessary, with one user infusing the fluid, and the other refilling syringes or operating the stopcock, and adequate fluid volumes are rarely achieved within the recommended time period.
Consider the example of a 40 kg child with traumatic injury and massive blood loss, who has a tibial IO needle as his only access. This child may require rapid infusion of 40-80 ml/kg of blood products, for a total of 1600-3200 ml. Repeated doses using a standard technique and 20 ml syringe would require 80-160 injections and the full attention of two healthcare workers, resulting in slow resuscitation and inefficient use of resources. The total infusion time could be 15-20 minutes, well outside the range of recommended rates, particularly in an actively bleeding child.